1. Field of the Invention
This invention is related to the field of video processing and, more particularly, to stabilizing a video.
2. Description of the Related Art
When a camera user captures a video sequence using equipment that is not as sophisticated as that used by professional movie production companies, the resulting video sequence typically includes a certain amount of “shakiness” that is caused by undesired camera motions. For example, the user's hand movements or walking motion, vibrations in a vehicle in which the user may be riding, or vibrations or imperfect movements of an apparatus to which the camera is mounted are all possible sources of undesired camera motions. The camera's motion through the three dimensional (3D) space can also be a source of undesired camera motion, e.g., due to the user walking an imperfect line, or riding in a vehicle that does not travel a straight line.
Some cameras have a built-in feature to attempt to compensate for unstable camera motions while the video is being captured. Typically, such cameras attempt to identify multiple points in the frames of the video and track those points from frame to frame. The cameras fit a motion model to the points, and apply an affine warp to the video based on the motion model. The cameras often also apply a low pass filter to the video to attempt to smooth the results. While the camera motion can be damped by such techniques, the resulting video still includes significant undesired camera motion. Additionally, the affine warp does not respect the content of the frames, often producing distortion in the images and particularly producing distortion in the most visually interesting objects in the video.
Buehler et al., “Non-Metric Image-Based Rendering for Video Stabilization”, proposed a mechanism for video stabilization that includes blending multiple frames from the video to produce an output frame. The Buehler mechanism works well for static scenes, but leads to ghosting and blurring of videos that include dynamic motion in the scene due to the blending of the multiple frames.